Elevator cars are installed in, for example, car frames which in turn are guided by rails fastened in elevator shafts and are moved up and down by drive engines by way of wire cables or other support means. Car floors, which are stiff in bending or stable relative to other mechanical actions, can be constructed in composite structure or sandwich mode of construction. A ‘sandwich’ floor of that kind has become known from, for example, EP 1 004 538 B1. The floor consists substantially of two mutually spaced-apart steel plates of a base structure, between which a support structure is arranged. The support structure is composed of a plurality of mutually crossing flat sections which form a grating-like composite structure. In practice it has proved that this floor stiff in bending does indeed withstand very high mechanical loads, but is comparatively costly and heavy.